Almost ready to start 68 LS1 Firebird, what jets for Holley HP 750?
#1
Almost ready to start 68 LS1 Firebird, what jets for Holley HP 750?
Ive been reading around these forums and similar forums to get an idea of what carburetor and jets i should get. I just bought the carburetor, from ebay, and from what i figured should be pretty close to what i need. Atleast close enough to start, test drive, and take the car through inspection.
The engine specs are in my sig, just a big cammed LS1 that will have heads on it onces it's all running, has good compression, tags... etc..
The carburetor is a Holley 750 HP. 3310 - 2 - vac secondaries. It has #72 primary jets and a #21 metering block which is equal to something like #75 jets. Has a 6.5 Power valve. Will this be close enough?
I plan on installing the LM-1 Wideband 02 sensor into the x pipe but i cant do that until i get it throguh inspection as an x pipe with side exits wont pass inespection so im using the flowmaster duals it had on it.
The car should be somewhere around 400rwhp or so right now seeing around 450rwhp with heads and new rockers/lifters and such. I will be driving it on the street.... mostly every day but to me driveability and fuel ecconomy really play no role.
The car should be just under 2900lbs as its completely stripped down. The rear end does have 4.56s but i will be running a 30" MT ET street radial on the road. The ignition is an MSD 6010 with MAP sensor so my timing is fully adjustable and i plan on adding extra timing for cruising speeds based on engine vac.
I also do plan on buying the conversion kit for the secondaries so i can change the jets out once i get my wideband installed.
The engine specs are in my sig, just a big cammed LS1 that will have heads on it onces it's all running, has good compression, tags... etc..
The carburetor is a Holley 750 HP. 3310 - 2 - vac secondaries. It has #72 primary jets and a #21 metering block which is equal to something like #75 jets. Has a 6.5 Power valve. Will this be close enough?
I plan on installing the LM-1 Wideband 02 sensor into the x pipe but i cant do that until i get it throguh inspection as an x pipe with side exits wont pass inespection so im using the flowmaster duals it had on it.
The car should be somewhere around 400rwhp or so right now seeing around 450rwhp with heads and new rockers/lifters and such. I will be driving it on the street.... mostly every day but to me driveability and fuel ecconomy really play no role.
The car should be just under 2900lbs as its completely stripped down. The rear end does have 4.56s but i will be running a 30" MT ET street radial on the road. The ignition is an MSD 6010 with MAP sensor so my timing is fully adjustable and i plan on adding extra timing for cruising speeds based on engine vac.
I also do plan on buying the conversion kit for the secondaries so i can change the jets out once i get my wideband installed.
#3
So since mines a 346 the smaller secondary jets would put me rought around the same area then right? so 12.8 is what you shoot for? I was going to set mine to more like a 13.8 haha i always thought 14:1 was ideal. My dynamic compression has to be extremely low with the size cam i am running anyway so i would thing that pinging wouldnt be as big an issue.
#5
A pic of it primed, not really any body work, 400/400 still in it, still had interior, 8.2 rear. I have pics of the engine and trans in, the rhino lined floor pans. The interior is completely gone right now ill be replacing it all with 26 gauge (or thinner) sheet aluminum panels im going to make, no rear seats, 4th gen camaro cloth seats. Nothing spectacular looking, just light weight.
I've photo documented everything i've done from the day i got the car, i just dont have much uploaded since i have dial up out here haha. I will definately be uploading a start up video though.
#6
It's not real pretty. It's going to be my daily driver and i have a driveway that's over a 1/4 mile long, all gravel, so there's not point in making anything 'prestine'. I still have to take off my crossmember and paint it. It started raining when i putting the last couple bolts in so i had to push it back into the trailer. Crossmember is a modified TH400 crossmember with 2x2x6 angle iron that bolts the front frame rail solid to the SFCS.
Last edited by Shawn MacAnanny; 04-09-2008 at 08:03 PM.
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#13
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just watch out with the edelbrock(msd) box, no matter what chip you use your timing will be over 35* at wot and most lsx engines dont like or need that much timing, most like 26-29* max wot
i had the edelbrock box but sold it and got the programmable msd 6010 box now my timing curve is correct
i had the edelbrock box but sold it and got the programmable msd 6010 box now my timing curve is correct
#14
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just watch out with the edelbrock(msd) box, no matter what chip you use your timing will be over 35* at wot and most lsx engines dont like or need that much timing, most like 26-29* max wot
i had the edelbrock box but sold it and got the programmable msd 6010 box now my timing curve is correct
i had the edelbrock box but sold it and got the programmable msd 6010 box now my timing curve is correct
#15
Ive heard of a few people having problem with the edelbrock boxes too as well. I just wonder if maybe those people got sent the wrong timing pills or something or had miss labeled pills. I'm going with the MSD box primarily because my setup will most likely change monthly and i want the 2 step for nitrous plus the mapable timing should i decide to go FI when my bottom end goes.
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go to the msd.com site and sign up on their forum,, the msd tech comes right out and says they built the edelbrock box to edelbrocks specs and they have no idea why edelbrock wanted those timing specs, and no matter what chip you use they all max out at 36* timing
36* timing wot on a lsx engine is almost guaranteed to rattle
36* timing wot on a lsx engine is almost guaranteed to rattle
#18
i had "rattle" on anything higher than pill no1 on uk fuels on the dyno. swapped to the 6010 and made my own version of a map someone on here gave me, 29 deg max and it made 412bhp@ hubs. shawn- i can send you a copy of mine if you like just drop me an email, but its something like 18deg around 1000rpm and 23 deg at the 2,200rpm area, then 29 deg from 3000rpm up.
i also added in upto 10 deg under vacuum at idle to clean it up which worked, nothing added on full throttle obviously.
i also added in upto 10 deg under vacuum at idle to clean it up which worked, nothing added on full throttle obviously.
#19
Hey thanks Chris! My email is ShawnMacAnanny@earthlink.net. I still cant believe how much power you are making cam only with a mild cam. That's incredible!